1. Field of the Invention
The present invention relates generally to the detection of ions utilizing ion-selective electrodes. More particularly, the present invention involves the discovery of a new group of ionophores which may be used in the ion-selective membranes that form an essential component of any ion-selective electrode.
2. Description of Related Art
Ion-selective electrodes are widely used in analytical chemistry to measure the concentration of specific ionic substances in fluids. Ion-selective electrodes have been used in a variety of potentiometric ion determinations in fluids ranging from drinking water to biological fluids, such as whole blood, plasma, serum and urine. Typical ions which have been measured using ion-selective electrodes include sodium, calcium, iodide, magnesium, potassium, chloride, and lithium. Generally, ion-selective electrodes are composed of an ion-selective membrane, an internal filling solution or electrolyte and a reference electrode. The ion-selective membrane is an essential element of every ion-selective electrode. Ion-selective membranes are typically formed from a plasticized polymer matrix in which an ionophore selective for the ion or ions of interest is dispersed. U.S. Pat. Nos. 4,995,960, 5,607,567 and 5,531,870 disclose exemplary ion-selective electrodes which utilize polymer matrix membranes which include a variety of different ionophores. Although numerous ionophores have been developed and are presently in use, there is a continuing need to find and develop new ionophores which have desirable ion selectivity when incorporated in a suitable membrane.
Mercuracarborands are a group of compounds which were discovered in the early 1990s and have been investigated for use as possible catalysts. This new class of macrocyclic multidentate Lewis acids are described in detail in the following references: Zheng et al., "Stnicture and Bonding of a Novel Mercuracycle Complex Containing B--Hg Bonds at Carboranc Vertices," Inorgainic Chemistry, Vol. 34, No. 2, 1995, 432-435; Yang et al., "Host-Guest Chemistry of a New Class of Macrocyclic Multidentatc Lewis Acids Comprised of Carboranc-Supported Electrophilic Mercury Centers," J Am. Chem. Soc. 1994, 116, 7142-7159; Yang et al., "`Anti-Crown` Chemistry: Synthesis of [9]Mercuracarborand-3 and the Crystal Structure of Its Acetonitrile Complexes," J Am. Chem. Soc., Vol. 115, No. 1, 1993, 193-195; Zheng et al., "Stereoselective Anion Template Effects: Syntheses and Molecular Structures of Tetraphenyl [12]Mercuracarborand-4 Complexes of Halide Ions, J Am. Chem. Soc., Vol. 117, 1995, 5105-5113; Zheng et al., "Hydrocarbon-Soluble Mercuracarborands: Syntheses, Halide Complexes, and Supramolecular Chemistry," Inorganic Chemistry, Vol 35, 1996, 1235-1243; Zinn et al., "A Hexamethyl Derivative of [9]Mercuracarborand-3: Synthesis, Characterization, and Host-Guest Chemistry," J Am. Chem. Soc., Vol. 118, 1996, 70-74. Although mercuracarborand compounds have been synthesized and studied extensively, there has been no investigation of their possible use as ionophores in ion-selective membranes.
The above-cited articles, as well as all of the other patents and references referred to in this specification, are hereby incorporated by reference.